CXCL12 and atherosclerosis: After platelet activation, a large amount of stromal cell-derived factor-1 can be expressed, which may induce CD34+ stem cells to differentiate into macrophages and foam cells, leading to leukocyte chemotaxis toward vascular endothelial cells in concert with monocyte exudation and formation of foam cells under the vascular intima, thereby causing atherosclerosis [31].